Solvent and substituent effects on azohydrazone tautomerism of some arylazo pyridone dyes

Abstract

Disperse monoazo dyes having pyridones as the coupling component exhibit azo- hydrazone tautomerism [1,2]. nI this work, ten dyes having the same 1-ethyl-4-methyl-6- hydroxy-3-cyano-2-pyridone have been synthesized (Fig. 1) and fully characterized by melting point, FTIR, H' and C31 NMR spectroscopy. Solvatochromism and tautomerism of these dyes have been investigated ni twenty one solvents of different polarity. The effects of specific and non-specific solvent/solute interactions on the position of their UV/Vis absorption bands have been evaluated using the Kamlet-Taft and Catalán solvent parameter sets. Furthermore, the effects on the solvatochromic behaviour of different substitution patterns on the aryl moiety have been examined.